One careful study gave people either caffeine or a placebo straight after they'd looked at a set of pictures. The caffeine group told the pictures apart from near-copies better the next day. The effect was on storing the memory, not on recalling it, and more caffeine wasn't better. Evidence: decent
Single study, 200 milligrams, people who didn't normally drink coffee. If you have three a day already, this probably does nothing for you. If you're a light drinker, it costs nothing to time the one you'd have anyway. Evidence: worth trying
Not after 2pm. Sleep matters more.
Same theme: Learning it
Learning it
Hook the new thing to something you know
Learning a name, a fact, a process: ask what it reminds you of, and tie it there.
no timeEvidence: decent
Learning it
Learn it last thing before lights out
The thing you need to remember goes in the final fifteen minutes before sleep. Not the phone.
15 minEvidence: decent
Learning it
Make it about you
Before you try to remember something, ask "when has this happened to me?" and answer in one sentence.
no timeEvidence: solid